The present invention relates to an apparatus and method for processing objects loaded in a reaction chamber while being heated with a heater; and, more particularly, to a heat treatment apparatus and method applicable to, e.g., an oxidation and diffusion processes for semiconductor wafers (hereinafter, referred to as wafers) having semiconductor integrated circuits (ICs) therein, a carrier activation process after ion implantation, a reflow process for planarization, an annealing process and a film forming process by thermal CVD reaction.
In a method for fabricating an IC, a vertical batch type hot-wall heat treatment apparatus (hereinafter, referred to as a vertical heat treatment apparatus) has been widely used in performing a heat treatment process on wafers. Such a vertical heat treatment apparatus includes a vertically disposed process tube provided with an inner tube, defining a reaction chamber therein, into which the wafers are loaded, and an outer tube surrounding the inner tube. Further included in the vertical heat treatment apparatus is a heater for heating the inside of the process tube, which is installed to the outside of the process tube, wherein a plurality of the wafers that are vertically stacked in a boat are loaded into the inside of the inner tube through a furnace mouth formed at the bottom thereof, and then the inside of the reaction chamber is heated to perform the heat treatment for the wafers.
In particular, some vertical heat treatment apparatuses are provided with a sub-heater at the bottom portion of the reaction chamber where large heat loss occurs, expediting the heat treatment process of the wafers by enabling temperature recovery and stability in a timely manner. However, such apparatuses suffer from its inability to rotate, which leads to deterioration of uniformity in thickness of thin film on a wafer (i.e., intra-wafer nonuniformity in film thickness). As a result, there has been proposed another type of vertical heat treatment apparatus, as disclosed in Japanese Patent Application Laid-Open Nos. 2001-156005 and 2001-210631, which include the sub-heater and a device for rotating the boat in order to improve intra-wafer uniformity in temperature as well as inter-wafer uniformity in temperature.
The vertical heat treatment apparatus disclosed in the former includes an insulating unit which is fixed on a cover and disposed between a boat and the cover for closing the lower end of the process tube, and a rotatable shaft for rotating the boat, which axially penetrates the center portion of the insulating unit. Disposed on the upper portion of the insulating unit is a sub-heater and disposed in the rotatable shaft are feeding lines for supplying electricity to the sub-heater.
Further, in the vertical heat treatment apparatus disclosed in the latter, an insulating body is disposed on a turntable for rotating the boat, and a sub-heater arranged in a planar shape is installed in the upper portion of the insulating body.
However, such a vertical heat treatment apparatus disclosed in Japanese Patent Application Laid-Open No. 2001-156005, has certain deficiencies. For instance, by forming a hole in the central portion of the sub-heater, through which the rotatable shaft passes, the sub-heater does not provide a sufficient amount of heat to the central portion of the wafers held in the boat, thereby significantly deteriorating intra-wafer uniformity in temperature distribution. Further, the rotatable shaft penetrating the insulating unit, is slenderly formed in order to reduce the above-mentioned side effects, entailing limitations in stably supporting a heavy boat.
In addition, the vertical heat treatment apparatus disclosed in Japanese Patent Application Laid-Open No. 2001-210631, has a problem of requiring a slippage ring in rotating the insulating body.
It is therefore, an object of the present invention to provide a vertical heat treatment apparatus capable of improving intra-wafer and inter-wafer uniformities in temperature, while performing a heat treatment process on wafers held in a boat.
In accordance with one aspect of the invention, there is provided a heat treatment apparatus including: a vertically disposed process tube defining a reaction chamber therein; a main heater for heating the reaction chamber, the main heater being disposed outside of the process tube; a boat for holding a plurality of wafers, the boat being loaded into and unloaded from the reaction chamber; and a boat rotating device for rotating the boat; wherein the boat rotating device includes a rotatable hollow shaft assembly and a fixed shaft coaxially disposed inside the rotatable hollow shaft assembly, and wherein a sub-heater is attached to an upper end of the fixed shaft, and the boat and an insulating portion are disposed on the rotatable hollow shaft assembly.
In accordance with still another aspect of the invention, there is provided a heat treatment apparatus including: a vertically disposed process tube defining a reaction chamber therein; a main heater for heating the reaction chamber, the main heater being disposed outside of the process tube; a revolving insulating unit; and a boat for holding a plurality of wafers, the boat being loaded into and unloaded from the reaction chamber, the boat being disposed on the revolving insulating unit and rotated therewith; wherein a horizontal circular portion of a sub-heater is fixedly installed inside the revolving insulating unit or an upper part thereof, and one or more feeding lines for supplying electricity to the sub-heater are provided substantially along a rotational axis of the boat.
In accordance with still another aspect of the invention, there is provided a method for fabricating semiconductor devices, including the steps of: loading a plurality of wafers into a boat; loading the boat into a reaction chamber of a vertically disposed process tube; heating the plurality of wafers with a sub-heater installed on a fixed shaft aligned with respect to a vertical axis of the boat while rotating the boat with a rotatable hollow shaft assembly disposed outside the fixed shaft, during or after loading the boat into the reaction chamber; processing the plurality of wafers by supplying one or more processing gases to flow into the reaction chamber when a temperature thereof reaches a treatment temperature; reducing the temperature of the reaction chamber; unloading the boat from the reaction chamber; and discharging the plurality of wafers from the boat.
The above and other objects and features of the present invention will become apparent from the following description of preferred embodiments given in conjunction with the accompanying drawings, in which:
FIG. 1 illustrates a vertical cross sectional view of a vertical heat treatment apparatus in accordance with a first preferred embodiment of the present invention;
FIG. 2 provides a perspective view of a boat rotating device, insulating plates and a sub-heater included in the vertical heat treatment apparatus of the first preferred embodiment;
FIG. 3 provides a cross sectional view of the boat rotating device, the insulating plates and the sub-heater included in the vertical heat treatment apparatus of the first preferred embodiment;
FIG. 4 sets forth a horizontal cross sectional view of the sub-heater taken along the line IVxe2x80x94IV in FIG. 3;
FIG. 5 describes a plurality of insulating plates of the present invention; and
FIG. 6 presents a partial vertical cross sectional view of a heat treatment apparatus in accordance with a second preferred embodiment of the present invention.